According to the related statistics, the construction cost of asphalt concrete pavements accounts for ¼-⅓ of the total construction cost of highways. Most maintenance cost is used for the pavements, and the asphalt concrete pavements generally have two main technical and quality defects. One defect is poor durability. The longer service life of the current domestic asphalt concrete pavements is from 8 to 12 years, and is generally shorter than 15 to 20 years of the designed service life; some pavements even need to be integrally reconstructed in 3 to 5 years. The other defect is that the pavements are seriously destroyed in early phase of use. Some new highways need to be maintained because pot holes, cracks, furrows and insufficient skid resistance, etc., occur only after the new highways are used for 1-3 years, or 6 to 8 years as the longer service life.
The preventive maintenance process is a systematic process of taking a series of maintenance measures in the life cycle of the asphalt concrete pavements. The preventive maintenance can improve the highway conditions, increase the driving quality, extend the pavement service life, reduce the life cycle cost, and can use an economic and effective mode to extend the pavement service life and improve the highway system performance.
Research indicates that the benefit-cost ratio of the preventively maintained pavements is from 6 to 10 times of that of the pavements without taking any maintenance measures. Related data shows that the performance of a qualified highway is reduced by 40% within 75% of the service life, and this stage is called preventive maintenance stage. If the highway is not maintained in time in this stage, its performance will be reduced by 40% once again within the following 12% of the service life, while the maintenance cost will be added by 3 to 10 times. After the asphalt pavement is preventively maintained, the cost can be saved for about 70%.
The asphalt mixture is a typical visco-elasto-plastic material, and mainly represents as a viscoelastic body within the range of actual operation, and represents as a visco-elasto-plastic body during construction compaction. The inelasticity of the material is mainly represented by non-recovery of deformation after unloading, namely the plasticity and the instantaneous non-recovery are the viscosity or elasticity aftereffect. Any visco-elasto-plastic material has rheological behavior, its rheological behavior and destructive behavior are related to time or temperature; the intensity and modulus will be rapidly reduced with temperature rise, and the furrow deformation resistance will be reduced. Thus, under the conditions of channelized traffic and heavy-loaded traffic of the existing highway, the furrows and other defects appearing on the pavements after a period of time are unavoidable.
The highway network of China has basically been built and will be completely maintained soon. As the new construction of the highway, maintenance requires a whole set of advanced technology. With the quick and harmonious development of the national economy, the number of highway vehicles in China is increased with time, and the highway pavements face serious challenges from the large-size vehicles and serious overloading vehicles. The effective service life of the existing highways generally cannot achieve its designed service life, and early serious damage often appears on the highway when it is only used for 1 to 3 years. Under the condition of serious shortage of cost for highway construction and maintenance, studying the preventive maintenance process for the asphalt pavement has especially crucial practical significance.
There are mainly two defects appearing on the asphalt concrete pavements of the current highways: 1, furrows and particularly serious furrows existing in the heavy-loaded vehicle lanes, because of large-size vehicles and serious overloading vehicles; 2, asphalt peeling because of ageing of asphalt, and insufficient adhesive force between asphalt and granular materials, insufficient degree of compaction of the asphalt pavement, micro cracks caused by large void fraction, chaps, check cracks, looseness, pitting surfaces, water seepage, etc.
For controlling the two early serious defects, the common method, which is milling first and then repaving, greatly wastes the resources of non-renewable stone and imported asphalt, and seriously pollutes the environment. The micro-surface treatment technique is used for partial highway sections. The micro-surface treatment technique is a cold mixing construction technique, which uses the macromolecular improved emulsified asphalt as a binding material and uses the thin layer technique as a main technique. In the technique, the polymer improved emulsified asphalt, the coarse and fine materials, the filling materials, water, additives and other materials are mixed into a slurry mixture in accordance with the designed proportion; the mixture is paved on the original pavement to form a thin layer with high skid resistance and durability, and the highway can be used soon. The micro-surface treatment technique has good water-preventing effect, can effectively prevent the water damage of pavement from occurring and developing, and can reverse the passive situation of continued need to repair pavement pot holes. The technique is mainly used for establishing and recovering the highway surface function, so that the highway is formed with a surface function layer with the advantages of water prevention, skid resistance, abrasion resistance and durability. However, the technique also has obvious defects, such as appearance bumps like the blemish scars, loud driving noise, and botchy appearance if peeling occurs.
The asphalt rejuvenator agent is a product for improving the performance of the aged asphalt through the chemical reaction between asphalt rejuvenator agent and asphalt. The stock solution of the asphalt rejuvenator agent is a low-concentration liquid with high fluidity. In the field test, the hairy tiny cracks are preferably treated by the asphalt rejuvenator agent, the asphalt rejuvenator agent can penetrate into the inside of the hairy cracks, and the stock solution of the asphalt rejuvenator agent can continually penetrate into the cracks if the cracks are deeper. The asphalt rejuvenator agent has the following characteristics: 1. water resistance: water penetration test indicates that the water penetration quantity of the pavement treated by the asphalt rejuvenator agent can be reduced by 90%; 2. high fluidity: the asphalt rejuvenator agent can be used for treating the cracks with the width of less than 5 mm; before the crack width is less than 5 mm, it is impossible to maintain the pavement by milling and repaving, and it is difficult to fill hot asphalt in the tiny cracks; the concentrated solution or diluents of the asphalt rejuvenator agent is used for treating the cracks to achieve the effects of convenience, economy and obvious effects; 3. adhesiveness: the asphalt rejuvenator agent is the material of the same kind as asphalt, is preferably combined with asphalt by chemical reaction, and enables the aged asphalt to obtain regeneration; 4. penetrability: the penetrability of the asphalt rejuvenator agent depends on the size of the void fraction of the asphalt concrete and the degree of dilution of the asphalt rejuvenator agent.
At present, the main applications of asphalt rejuvenator agent include: 1. directly spraying on the asphalt concrete surface to form a spraying layer. This mode is simple, but will obtain poor repair effects, such as poor integrity, inability to repair the lower frame damage, poor surface flatness and the like, if heat treatment is not performed; 2. Adding the asphalt rejuvenator agent after crushing the original asphalt concrete, and mixing by heating method or cooling method to obtain regeneration. The mode destroys the pavement.
The asphalt concrete pavement maintenance is a significant and difficult issue before people. People try to provide effective modes for maintaining the asphalt concrete pavement, such as using asphalt rejuvenator agent, etc. However, the ingredient components of the existing asphalt concrete pavements determine that the existing asphalt concrete pavements are difficult to be effectively maintained under the instruction of the existing method.
Therefore, those skilled in the art are eager to find an effective maintenance process which is suitable for asphalt concrete pavements to meet more and more maintenance requirements of the asphalt concrete pavements.